The Crown claims Stephen George Russell was driving in a dangerous manner before the crash on the Oxley Highway on January 3, 2019.

Lynette Marie Russell, 72, who was in the front seat, and 38-year-old Stephen Leslie Russell, who was in the back seat, died at the scene as a result of their injuries.

Another passenger in the backseat was seriously injured and airlifted to hospital.

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Russell was due to defend the charges at trial in Tamworth District Court this week after pleading not guilty, but it's been vacated.

The court heard the defence filed a notice of motion in Armidale District Court last week, which was unopposed by the Crown, court documents stated.

After hearing the application, the judge granted the notice of motion and vacated the trial date, adjourning the case to this week to find a new date in Tamworth court.

Solicitor Peter Schmidt appeared without his client who he said was "in the precincts of court".

Acting Judge Jonathan Williams was told the new trial would involve two experts "one for defence, one for the prosecution", Mr Schmidt said.

"We have asked for six weeks for an expert witness [report], and the prosecution is asking for three weeks in reply," Mr Schmidt said.

The court heard a another Tamworth trial fixed for mid-November might not go ahead because of the COVID-19 border closures between Victoria and NSW. The accused lives in Victoria, the court heard.

DPP solicitor Max Dickson said Russell's trial was "a significant matter".

"It is a sensitive matter," he told the court.

Russell's accused of four charges including two counts of dangerous driving occasioning death; dangerous driving causing grievous bodily harm; and doing an act with intent to pervert the course of justice.

"It's a matter in which two persons died," Mr Dickson said.

"It had not insignificant media attention in the local court.

"The families of the deceased persons are likely to be in attendance."

The court heard the trial is expected to run for more than a week, but current COVID measures mean significant restrictions on numbers in court could see family members refused entry.

"I'll stand the matter over," Acting Judge Williams told the court, adjourning the case to November.

"A seven-day estimate, with two expert witnesses.

"Bail's to continue."

If found guilty of the charge of dangerous driving occasioning death, Russell faces a maximum penalty of 10 years' imprisonment.

Russell, then 58, was allegedly driving a Toyota Prado towing a caravan when it struck a railing, rolled and slammed into a tree.

His wife and son died at the scene.

A 38-year-old woman, who was trapped in the wreckage of the crash for some time, suffered head and spinal injuries. She was also airlifted to Tamworth hospital.

Specialist crash investigators spent hours examining the scene, the Toyota Prado and the caravan.

After extensive investigations, Russell was charged by the Oxley Crash Investigation Unit in June last year and had his driver's licence suspended.

At the time, police said one dog died in the incident and another survived.

It's understood the family had set off from Tamworth and were headed east along the Oxley Highway.